Here's a brief intro from wikipedia : "A water jet cutter, also known as a water jet or waterjet, is an industrial tool capable of cutting a wide variety of materials using a very high-pressure jet of water, or a mixture of water and an abrasive substance. The term abrasive jet refers specifically to the use of a mixture of water and abrasive to cut hard materials such as metal or granite, while the terms pure waterjet and water-only cutting refer to waterjet cutting without the use of added abrasives, often used for softer materials such as wood or rubber." This week we're using a waterjet to cut through metal and stone. Here's what the waterjet looks like.
Here's the waterjet in action
Here's what the video looks comixified
Here's what you can create
Essentially, you flip three buttons. First, there's the power switch for the whole machine (computer, arm, everything). Then, there's a power switch for the computer. Then, there's a power switch for a generator. Once those are on, you pull up a 2d design, set the cut paths/size, orientation, material type, material width, and X,Y,Z origins. Then, you check how much abrasive material you need and fill up the abrasive material pouch. Then, you raise the water level. And click go.
For a final polish, like you see on the penguin and owl cutouts, you can head over to a sand blaster and pretty it up.